It is possible to alter a chemical reaction by changing the _________ of the chemicals involved.

• A. Concentration
• B. Temperature
• C. Pressure
• D. Volume

Answer: (B)

Changing temperature alters the energy of the molecules, which directly affects how easily they react. When temperature goes up, more molecules have enough energy to reach and overcome the activation energy, so the reaction proceeds faster. This relationship is captured by the Arrhenius equation and is a fundamental reason temperature is a powerful factor in reaction rates. Temperature can also shift the balance of products and reactants for reactions that release or absorb heat, moving the equilibrium toward the endothermic direction with higher temperature and toward the exothermic direction with lower temperature. Other factors like concentration, pressure, or volume influence reactions mainly by changing how often particles collide or how crowded they are, but they don’t change the energy distribution of the molecules the way temperature does.